21328440 has 64 divisors (see below), whose sum is σ = 73128960. Its totient is φ = 4874880.

The previous prime is 21328423. The next prime is 21328451. The reversal of 21328440 is 4482312.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21328440.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11856 + ... + 13535.

It is an arithmetic number, because the mean of its divisors is an integer number (1142640).

Almost surely, 2^21328440 is an apocalyptic number.

21328440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21328440 is an abundant number, since it is smaller than the sum of its proper divisors (51800520).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21328440 is a wasteful number, since it uses less digits than its factorization.

21328440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25412 (or 25408 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 24.

The square root of 21328440 is about 4618.2724042655. The cubic root of 21328440 is about 277.3233028198.

The spelling of 21328440 in words is "twenty-one million, three hundred twenty-eight thousand, four hundred forty".